Micro-motion acquisition method

Abstract

The present application provides a kind of microseismic acquisition method, comprising the following steps: S1: connect detector to seismograph by cable, arrange detector according to design;S2: start microseismic data measurement, obtain the microseismic data of one measuring point or one arrangement;S3: move detector to next measuring point or arrangement;S4: repeat the measurement of steps S2 and S3;S5: collect the measurement signal of each detector, calculate the distance between base point and measuring point according to the position coordinates of base point and measuring point;S6: the measurement data of base point and measuring point are cross-correlated in frequency domain, and the correlated trace gather is formed;S7: for the arrangement of n detectors, at least n-3 correlated trace gathers of arrangement can be extracted;S8: use correlated trace gather to extract dispersion curve, and carry out transverse wave velocity inversion and other result drawing.The present application realizes the cross-correlation of linear arrangement or array in working area through base point measurement, improves the calculation accuracy of dispersion curve between array, and achieves the purpose of fine detection.

Description

TECHNICAL FIELD

[0001] The present application relates to a microtremor acquisition method, mainly applied to the detection of geological anomaly bodies with obvious density and wave velocity differences between underground media, suitable for measuring underground wave velocity anomaly bodies, suitable for fine detection of shallow spaces such as goaf, fault, cavity, boulder, etc., and suitable for projects with high requirements for detection speed, depth and precision of underground structures and structures. BACKGROUND

[0002] The microtremor method is a geophysical method that uses a seismograph to acquire vibration signals from natural phenomena such as earthquakes, ocean waves, wind, tidal changes, lightning, and human activities such as mining and mechanical operation, and uses microtremor signals to conduct underground structure detection.

[0003] Microtremor detection is to calculate the frequency and phase velocity (dispersion curve) of the vertical component of the microtremor signal recorded by the seismograph, and to obtain the wave velocity structure of the underground medium by inverting the dispersion curve, so as to achieve the reconstruction of the velocity of the underground medium. With the continuous development of detection methods and technologies, it has been widely used in geological structure detection, geothermal investigation, goaf, karst and other fields, and has achieved a large number of successful cases.

[0004] The commonly used microtremor observation device at present mainly has the following several kinds: nested triangle, cross, L shape, circle, rhombus and straight line type station. The main problems and shortcomings are as follows: (1) the station device is complex, and the data acquisition efficiency is low; (2) the station is difficult to set up in complex terrain areas; (3) the anti-fixed vibration interference ability is poor, and the high-frequency vibration or noise near the site has a great influence on the microtremor original data; (4) since the detection depth of the microtremor is proportional to the size of the array side length, the detection depth of the array in complex terrain areas is limited.

[0005] Due to the characteristics of the device itself, it is difficult to extract the dispersion curve by simple processing of the array and straight line type device, and it is difficult to obtain the true reconstructed velocity structure of the underground medium. SUMMARY

[0006] The present application aims to provide a microtremor acquisition method to overcome the shortcomings of the prior art.

[0007] To this end, the above-mentioned purpose of the present application is realized by the following technical scheme:

[0008] A microtremor acquisition method, characterized in that the microtremor acquisition method comprises the following steps:

[0009] S1: connecting the geophone to the seismograph through the cable, and arranging the geophone according to the design;

[0010] S2: start microtremor data measurement to obtain microtremor data of one measuring point or one arrangement;

[0011] S3: move the detector to the next measuring point or array;

[0012] S4: repeat the measurement of steps S2 and S3;

[0013] S5: collect the measurement signals of each detector, and calculate the distances Δx1, Δx2, Δx3, Δx4, …, Δx n , between the base point and the measuring points according to the position coordinates of the base point and the measuring points;

[0014] S6: the measurement data of the base point and the measuring points are cross-correlated in the frequency domain to form a cross-correlated gather;

[0015] S7: for an array with n detectors, at least n-3 cross-correlated gathers of the array can be extracted;

[0016] S8: use the cross-correlated gather to extract the dispersion curve and draw the result map such as the S-wave velocity inversion.

[0017] While the above technical solutions are adopted, the present application can also adopt or combine the following technical solutions:

[0018] As a preferred technical solution of the present application: a straight line type equidistant array is adopted, which simplifies the calculation in two-dimensional space and improves the quality of the dispersion curve.

[0019] As a preferred technical solution of the present application: a node type seismograph is adopted to improve the construction speed and avoid data distortion.

[0020] As a preferred technical solution of the present application: the number of nodes in the array is increased to obtain data of different detection depths by combining data of node seismographs with different spacings, thereby improving the accuracy of the results.

[0021] The present application provides a micro-motion acquisition method, which realizes the cross-correlation of linear arrays or arrays in a work area through base point measurement (virtual seismic source), improves the calculation accuracy of the dispersion curve between arrays, and achieves the purpose of fine detection. The micro-motion acquisition method provided by the present application can be applied to fine detection of geological bodies with obvious wave velocity anomalies such as underground cavities, faults, and surrounding media. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The physical architecture diagram involved in the micro-motion acquisition method provided by the present application.

[0023] Figure 2 It is a schematic diagram of the micro-motion measuring point arrangement of the mountainous steep slope.

[0024] Figure 3 It is the actual gather data of detectors 1-3.

[0025] Figure 4 Cross-correlation gather of geophones 2 / 3 with geophone 1 as base point.

[0026] Figure 5 Dispersion curve extracted from cross-correlation gather of geophones 2 / 3 with geophone 1 as base point. DETAILED DESCRIPTION

[0027] The present application provides a microseismic acquisition method, comprising the following technical solutions:

[0028] 1) Background noise data is acquired by setting base stations;

[0029] 2) Fixed vibration interference signals are suppressed by arranging cross-correlation calculation with base points;

[0030] 3) Precise point measurement is performed on each station during station layout to obtain relative coordinates for subsequent extraction of dispersion curves between stations;

[0031] 4) Station rolling measurement can be performed according to depth measurement requirements and the number of stations, and cross-correlation calculation is performed between base points and measurement points in each time period, so that the base point can be moved or fixed in a work area.

[0032] The present application is described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] A microseismic acquisition method, characterized in that the microseismic acquisition method comprises the following steps:

[0034] S1: Connect geophones to a seismograph through a cable, and arrange the geophones (or node seismographs) according to design;

[0035] S2: Start microseismic data measurement to obtain microseismic data of one measurement point or one arrangement;

[0036] S3: Move the geophones (or node seismographs) to the next measurement point or arrangement;

[0037] S4: Repeat the measurement of steps S2 and S3;

[0038] S5: Collect measurement signals of each geophone (or node seismograph), and calculate distances Δx1, Δx2, Δx3, Δx4, …, Δx n , between the base point and the measurement points according to the position coordinates of the base point and the measurement points;

[0039] S6: Perform cross-correlation on the measurement data of the base point and the measurement points in the frequency domain to form a cross-correlated gather;

[0040] Figure 2 As a schematic diagram of arrangement on mountain steep slope, the geophone 1 can be used as a base point to make cross-correlation with the geophone 2 and the geophone 3, so as to obtain two gathers relative to the base point geophone 1, which are used for extracting the dispersion curve; the geophone 2 can be used as a base point to make cross-correlation with the geophone 3 and the geophone 4, so as to obtain two gathers relative to the base point geophone 2, which are used for extracting the dispersion curve; in sequence, the last geophone 11 can be used as a base point to make cross-correlation with the geophone 12 and the geophone 13, so as to obtain two gathers relative to the base point geophone 11, which are used for extracting the dispersion curve;

[0041] S7: for the arrangement of n geophones (or node seismographs), at least n-3 cross-correlation gathers of the arrangement can be extracted;

[0042] S8: the dispersion curve is extracted by using the cross-correlation gather, and the result map such as the inversion of the wave velocity of the shear wave is drawn.

[0043] As a preferred, it is suggested that a linear type equal-interval arrangement is adopted, in a two-dimensional space, the calculation is simplified, and the quality of the dispersion curve is improved.

[0044] As a preferred, it is suggested that the node type seismograph is adopted, the construction speed can be improved, and the data distortion caused by the leakage of the seismic cable and the like is avoided.

[0045] As a preferred, it is suggested that the number of nodes in the arrangement is increased, the data of different detection depths can be obtained by combining the data of the node seismographs with different intervals, and the precision of the result is improved.

[0046] Figure 3 The abscissa is a time axis, and the ordinate is a geophone number. Figure 3 In the waveform diagram, the gather data of three continuous arranged geophones selected by the device is shown. Figure 3 The continuous waveforms on the waveform diagram are the basis for data analysis, and for the arrangement of n geophones, at least n-3 gather data can be extracted.

[0047] Figure 4 The abscissa is a time axis, and the ordinate is a geophone number. Figure 4 Figure 3 The data is the gather data calculated by using the cross-correlation algorithm. The first channel is used as a reference, the second channel is compared with the first channel to make correlation, and the third channel is compared with the first channel to make correlation, so as to obtain the waveform diagram of the correlation data.

[0048] Figure 5 The abscissa is a phase velocity, and the ordinate is an extraction frequency. Figure 5 The abscissa is a phase velocity, and the ordinate is an extraction frequency. Figure 4 The dispersion curve is calculated by using the spatial cross-correlation of the gather.

[0049] ​The above detailed description is merely exemplary in nature and is not intended to limit the application as described herein. Any modification or equivalent arrangement within the spirit or scope of the application should be considered to fall within the scope of the application.

Claims

1. A micro-motion acquisition method, characterized in that: The microtremor acquisition method comprises the following steps: S1: connecting the geophone to the seismograph through a cable, arranging the geophone according to the design; S2: starting the microtremor data measurement to obtain the microtremor data of one measuring point or one array; S3: moving the geophone to the next measuring point or array; S4: repeating the measurement of steps S2 and S3; S5: collecting the measurement signals of each geophone, and calculating the distance between the base point and the measuring point according to the position coordinates of the base point and the measuring point; S6: performing cross-correlation on the measurement data of the base point and the measuring point in the frequency domain to form the cross-correlated trace gather, including cross-correlating the geophone 1 with the geophone 2 and the geophone 3 to obtain two trace gathers relative to the base point geophone 1 for extracting the dispersion curve; cross-correlating the geophone 2 with the geophone 3 and the geophone 4 to obtain two trace gathers relative to the base point geophone 2 for extracting the dispersion curve; and sequentially cross-correlating the geophone n-2 with the geophone n-1 and the geophone n to obtain two trace gathers relative to the base point geophone n-2 for extracting the dispersion curve; S7: for an array with n geophones, at least n-3 cross-correlated trace gathers of the array can be extracted; S8: extracting the dispersion curve by using the cross-correlated trace gather, and drawing the inverted result graph of the shear wave velocity.

2. The micro-motion acquisition method of claim 1, wherein: The linear equidistant array is adopted to simplify the calculation in the two-dimensional space and improve the quality of the dispersion curve.

3. The micro-motion acquisition method of claim 1, wherein: The node-type seismograph is adopted to improve the construction speed and avoid data distortion.

4. The micro-motion acquisition method of claim 1, wherein: The number of nodes in the array is increased to obtain data of different detection depths by combining the data of the node seismographs with different spacings, thereby improving the accuracy of the result.

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